Method of making magnetic transfer sheet and article

ABSTRACT

Carbon paper coatings of the type embodying a vinyl resin matrix which embraces a pigment-carrying nonvolatile liquid exudable under pressure to make a mark on a copy sheet, are provided. The coating is of such character that pigments having a high agglomerative tendency, especially magnetic pigments such as iron oxide, can be used and still be carried properly from the layer along with the liquid vehicle when pressure is applied. In the case of magnetic pigments this makes it possible to provide marks which embody sufficient pigment to give appropriate signal strength for scanning. The result is achieved by including in the mixture an amine type wetting agent, and by providing as a portion of the volatile vehicle used to render the mixture coatable a pair of control solvents of different types. The control solvents are one of the ketone type and the other of a nonketone type (such as ethyl acetate, 2-nitro propane, or equivalent). The optimum ratio between the control solvents is usually between about 1:2 and about 1:1.

United States Patent [72] Inventor James E. Deegan Euclid, Ohio [21] Appl. No. 746,194 [22] Filed July 19, 1968 [45] Patented Nov. 9, 1971 [73] Assignee Addressograph-Multigraph Corporation Cleveland, Ohio [54] METHOD OF MAKING MAGNETIC TRANSFER SHEET AND ARTICLE 8 Claims, 2 Drawing Figs.

[52] U.S. Cl 117/235,

117/361, 252/6254, 252/6256, 260/23, 260/41 [51] Int. Cl R4lm 5/10 [50] Field oISearch..... l17/36.l,

[56] References Cited UNITED STATES PATENTS 2,944,037 7/1960 Clark ll7/36.1 2,992,121 7/1961 Francis etal. 117/361 3,467,539 9/1969 Schlotzhauer et al. 117/361 3,496,015 2/1970 Newman etal. 117/361 Primary Examiner-Murray Katz ABSTRACT: Carbon paper coatings of the type embodying a vinyl resin matrix which embraces a pigment-carrying nonvolatile liquid exudable under pressure to make a mark on a copy sheet, are provided. The coating is of such character that pigments having a high agglomerative tendency, especially magnetic pigments such as iron oxide, can be used and still be carried properly from the layer along with the liquid vehicle when pressure is applied. In the case of magnetic pigments this makes it possible to provide marks which embody sufficient pigment to give appropriate signal strength for scanning. The result is achieved by including in the mixture an amine type wetting agent, and by providing as a portion of the volatile vehicle used to render the mixturecoatable a pair of control solvents of different types. The control solvents are one of the ketone type and the other ofa nonketone type (such as ethyl acetate, 2-nitro propane, or equivalent). The optimum ratio between the control solvents is usually between about 1:2 and about 1:1.

METHOD OF MAKING MAGNETIC TRANSFER SHEET AND ARTICLE This invention relates to ink compositions or pastes containing agglomerative pigments such as magnetic iron oxide for use in the production of carbon papers, and carbon papers prepared using such compositions. An example of such a composition employing a waxy base and a magnetic pigment is given in U.S. Pat. No. 2,744,031, issued May 1, 1956. The product resulting from the teachings of this patent, however, is of only moderate utility since the image resulting from a transfer operation using this type of carbon layer 1) has a significant degree of fringe irregularity, and (2) is subject to disarrangement and smudging by subsequent handling to a signiticant degree. Inasmuch as most applications for magnetic carbon inscriptions call for sensing the transferred image with automatic equipment which can accurately discriminate only clear, sharp-edged images, the approach suggested in the said patent has enjoyed somewhat restricted commercial acceptance.

Efforts have been made to embody magnetic pigment particles in transfer layers of other than waxy material in an attempt to avoid one or the other or both of the above-mentioned drawbacks. One such approach has been to attempt to incorporate substantial amounts of magnetic pigment material in transfer compositions formulated in accordance with the principles taught in US. Pat. No. 2,820,717, issued Jan. 21, 1958. The layers produced by the process described in this disclosure consist of a resinous matrix which holds a substantially discontinuous oil-pigment phase, so arranged that the latter can be efiused, (i.e. squeezed from the matrix under writing blows or pressure) to form a mark on the copy sheet. For convenience this form of transfer operation will be referred to as a squeeze-out" transfer as opposed to the conventional waxy layers in which all or a fraction of the relatively homogeneous layer is separated and pressure-transferred to the copy sheet in the image area.

However, before the present invention, attempts in this direction have been unsuccessful. Not only did the resulting transfer layers prove too soft and oily for proper marking results, but it was found that the magnetic iron oxide pigment used would not transfer with the oil vehicle in any substantial quantity, so that the mark made lacked the requisite magnetic properties to produce adequate signal strength.

An object of the present invention is to overcome the aforesaid difficulties and to prepare an effective transfer composition and carbon paper of the squeeze-out type embodying an agglomerative pigment such as magnetic iron oxide.

This object has been achieved by including in the makeup of the transfer composition a material having wetting agent properties, and in most instances reducing materially the proportion of oil used in relation to the amount of resinous and pigment material present.

One difficulty encountered in attempting to introduce magnetic iron oxide pigment into a transfer formula of the squeeze-out type was, as noted above, the failure of the pigment to transfer to the copy sheet when pressure was applied to the coating. It is possible that this condition arose by reason of the pigments failure to remain properly dispersed in the oil of the composition, perhaps agglomerating within the pores of the resin matrix to form particles of excessive size, and therefore remaining behind in the pores as the oil is squeezed out. Whatever the explanation, it has been discovered that this transfer failure can be overcome, and that when a suitable wetting agent is introduced into the mixture, the oil, surprisingly, is caused to hold the pigment particles indefinitely in such condition that they transfer to the copy sheet with the oil in the same manner as do other pigment particles.

Suitable wetting agents for the composition in question are mainly those of the amine type with a fatty acid substituent. These are derived in many cases from natural products, and one example of a wetting agent which has proved particularly suitable is Duomeen TDO, a product of Armour Industrial Chemical Division, Armour & Company, which may be described as tallow 1,3-propylene diamine dioleate. This type of wetting agent may be used alone or in conjunction with other wetting agents or emulsifying agents of the type which are compounds of long chain fatty acids, e.g. diglycol laurate. In such case at least one-third of the wettingagent mixture should consist of the amine type wetting agent. These combined agents may be added in small amounts, for example, from about 1 percent up to about 33 IS percent of the oil used, to achieve the desired results.

In order to understand more fully the invention being described herein, reference may be had to the following table showing suggested appropriate ranges for the various ingredients:

Ingredients Parts by Weight (1) Solid synthetic polymer base (2) Nonvolatile liquid'softener, immiscible with the solid base (3) Agglomerative Pigment (4) Wetting Agent (5) Volatile liquid vehicle, solvent for both I) and 2) Amount sufficient to render the mixture readily coltahle (usually between about and I00).

The synthetic polymer is a vinyl chloride-acetate copolymer, or a copolymer mixture containing 85 percent to 95 percent vinyl chloride, (e.g. Vinylite VYHI'I, Vinylite VYLF, Vinylite VYNS and mixtures thereof).

'Ihe nonvolatile softener is generally any oil which is nondrying and nonvolatile and which will not significantly dissolve or react with the resinous material of the solid base. Castor oil is preferably used in this connection.

The pigment used is preferably powdered iron oxide, but may be any magnetic pigment such as finely divided iron or other metallic powder most of which have similar agglomerative tendencies. For best results, particle sizes in the range of aboutlQto 5 Q0 millimicrons should be used.

Depending upon the specific ingredients selected, there will be variations in the proportions needed to produce the best results. These will, however, be readily determined by those skilled in the art of carbon ink compounding having the present description and statement of principles as a guide.

Aspec ific illu s tfative eraiiie'miamsman according to the invention follows:

.; EXAMPLE Parts by Ingredients weight Solid base: Soft vinyl chloride acetate copolymcr 8588 percent vinyl chloride (mg. a mixture of Vinylite VYIIII, VY F, VYNS)... l0 Softener: Castor oil 10 Magnetic iron oxide pigmrnL. .27

Wetting agent:

Duomeen TDO 1 Diglycol laurate. l 1. 8

Total wetting agent 2. 8 Volatile liquid vehicle:

Toluene 32 Methyl ethyl ketone 7 Ethylaeetate 11 Total volatil0. 5O

Expressed in another way, the mixture of this example may be separated into two parts and the proportions expressed in percentages:

Percentage by weight of non- N on-volatilu ingredients volatiles Solid bas( 20. 1 Softcn0r 20.1 Pigment... 54. .2

EXAMPLE -Cominued Parts by Ingredients weight Wetting agent: A

Duomeen TDD... 2 5 Diglycol laurate 3. 6

Total Wetting agent 5.6

Total 100. 0

10 Percentage by weight of Volatile liquid vehicle volatiles Toluene 63 Methyl ethyl ketone Ethyl acetate 22 15 Total 100 A sufficient amount of the volatile liquid vehicle is mixed with the. nonvolatiles to provide a coatable mixture. A preferred portion employs in the neighborhood of equal parts by weight.

In connection with the foregoing example, it may be noted that, in addition to the hydrocarbon solvent, i.e. toluene, two other types of solvents are included which form a coacting pair of control solvents, and the relationship of these to each 25 other has been found useful in controlling the transfer action of the resulting transfer layer. By increasing the proportion of ketone-type solvent the layer can be made tougher and more resistant to transfer of color. By increasing the nonketone sol-' vent (i.e. ethyl acetate or equivalent, such as 2 nitro-propane) the amount of material transferred for a given pressure will be enhanced. The precise mechanism of this control action is not entirely understood, but it is believed that there may be a difference in the degree to which these solvents are retained by the vinyl resin of the matrix when the layer is dried.

For most situations a ratio of ketone solvent of ethyl acetate solvent (or equivalent) of between 1:2 and 1:1 will be found to be appropriate. The optimum for the particular example shown was found to be about 2:3.

The control solvents, due to cost, are normally kept to a 40 minimum proportion of the overall volatile solvent fraction, and are effective when they constitute about one-half or a little less of the total volatile liquid portion of the coating mixture.

When a composition prepared according to the formula shown in the foregoing example, or any equivalent variation thereof, is compounded in the usual manner and spread in a thin film upon a flexible support, e.g. paper, polyethylene, or other flexible film, and the volatile vehicle evaporated, there results a transfer layer of exceptional quality from which a mark inspired by writing pressure or a type blow may be readily transferred to a receiving or copy sheet.

When it is desired to provide a mark carrying an amount of magnetic pigment sufficient to give the desired signal strength for automatic sensing, it has been found that the most effective results are achieved when the layer, after casting, is dried by means of a high speed air stream impinging on the surface of the layer. This apparently provides a sheet whose surface is dry enough for normal handing and use without impairing the ability of the bulk of the layer to actively release the pigmentcarrying liquid under pressure. When magnetic pigments are. under consideration, this may be said to be one of more pivotal factors in providing layers which can make marks which will produce appropriate signal level without the layers being excessively soft and smudgy and prone to the production of spurious or extraneous marks.

The transfer layers prepared in accordance with this description lend themselves particularly well to use in applications where pressure transfer alone is to be used, although they will also prove operative in situations involving impact.

The mark thus produced is characterized by clean, sharp outlines and accordingly lends itself readily to automatic sensing by currently available equipment, and given particularly accurate results when thus employed.

In the latter connection, test samples were made by imprint- 75 ing characters through transfer sheets of different kinds upon equivalent copy sheet surfaces, using care to keep the operating conditions uniform. The resulting marks were then optically enlarged equal amounts and compared by inspection.

The improvenient achieved by the present invention is demonstrated in the accompanying drawing, the figures of which are precise copies of the enlargements above described.

In the drawing:

FIG. 1 is an enlargement of the mark made using a pressure responsive waxy transfer sheet of the type currently marketed for use in applications requiring magnetic pigment for automatic sensing.

FIG. 2 is an enlargement of the mark made using a pressure responsive transfer sheet of the type set forth in the foregoing description, and particularly with relation to the specific example, and illustrating the improved sharpness and edge regularity obtained.

From the foregoing description it can be seen that the present invention provides a novel and improved transfer element or carbon sheet capable of furnishing a mark of distinctly improved quality for automatic sensing purposes, and giving an effective deposit under pressure even with pigments which demonstrate severely agglomerative tendencies. The mark which can be made by this novel transfer layer is not only notable for the regularity of its edges as shown in the drawing, and is also characterized by a unique freedom from the danger of smudging, since no significant surface deposit is present after the effused oil has dried by absorption into the paper fibers which is virtually instantaneous.

Thus, while there has been illustrated and described preferred embodiments of the invention, it is emphasized that these are capable of variation and modification in a number of ways. The invention is not limited to the precise details set forth, but should be understood to include such changes and alterations as fall within the purview of the following claims.

What is claimed is:

l. A pressure responsive marking element comprising a foundation and a layer of a marking composition thereon, the composition comprising a porous resinous continuous phase and a fluent discontinuous phase including an oily liquid and a pigment, in which the composition consists essentially of:

10 parts by weight of substantially nonpressure transferable thermoplastic resin base of a soft vinyl chloride-acetate copolymer or mixture of such copolymers;

7 to 15 parts by weight of a nonvolatile liquid softener, im-

miscible with the base;

10 to 40 parts by weight of an agglomerative magnetic pigment; and 0.1 to 5 parts by weight of a wetting agent, a substantial share of which is a wetting agent of the amine type.

2. A marking element as set forth in claim 1 in which the amine type wetting agent is tallow 1,3-propylene diamine dioleate. 7 V i g n I 3. A marking element as set forth in claim 1 in which the layer of marking composition is the dried residue of a mixture embodying the ingredients stated in claim 1 together with a volatile liquid vehicle comprising a ketone and a nonketonic solvent of the ethyl acetate-2 nitropropane class, and in which the volatile vehicle contains these ingredients in a ratio of between 1:2and 1:1.

4. A marking element as set forth in claim 3 in which the dried layer is the result of treating the undried coating by impinging on its exposed surface a stream of air.

5. A marking element as set forth in claim 4 in which the amine type wetting agent is tallow l,3-propylene diamine dioleate. I I

6. A marking element as set forth in claim 5 in which the softener is castorbil and is present in an amount equal to about 10 parts by weight; the magnetic iron oxide pigment is present in an amount equal to about 27 parts by weight; and the wetting agent is present in an amount equal to about 2.8 parts by weight of which at least 1 part by weight is tallow 1,3- propylene diamine dioleate.

7. The method of preparing a pressure sensitive ink-releasing element which comprises coating a foundation with a thin 5 6 layer of a composition consisting essentially of: type; and

10 parts by weight of a substantially nonpressure transferaa volatile liquid vehicle which is a solvent for the base and Me thermoplastic resin base of a 50ft Vinyl chloride miscible with the softener in an amount sufficient to 3%? {"f p y mixture oiisuch p y iW render the mixture readily coatable. 7 I 15 P y weight of a nonVOlatile liquid Softener, 8. The method of preparing a pressure sensitive ink-releasmiscible with the base; ing element as set forth in claim 7 in which the setting of the 10 to 40 parts by weight of an agglomerative magnetic piglayer is abetted by causing a stream of air to impinge on the ment, 0.1 to 5 parts by weight of a wetting agent, a subexposed surface thereof. stantial share of which is a wetting agent of the amine 10 r I: w m 

2. A marking element as set forth in claim 1 in which the amine type wetting agent is tallow 1,3propylene diamine dioleate.
 3. A marking element as set forth in claim 1 in which the layer of marking composition is the dried residue of a mixture embodying the ingredients stated in claim 1 together with a volatile liquid vehicle comprising a ketone and a nonketonic solvent of the ethyl acetate-2 nitropropane class, and in which the volatile vehicle contains these ingredients in a ratio of between 1:2 and 1:1.
 4. A marking element as set forth in claim 3 in which the dried layer is the result of treating the undried coating by impinging on its exposed surface a stream of air.
 5. A marking element as set forth in claim 4 in which the amine type wetting agent is tallow 1,3-propylene diamine dioleate.
 6. A marking element as set forth in claim 5 in which the softener is castor oil and is present in an amount equal to about 10 parts by weight; the magnetic iron oxide pigment is present in an amount equal to about 27 parts by weight; and the wetting agent is present in an amount equal to about 2.8 parts by weight of which at least 1 part by weight is tallow 1,3-propylene diamine dioleate.
 7. The method of preparing a pressure sensitive ink-releasing element which comprises coating a foundation with a thin layer of a composition consisting essentially of: 10 parts by weight of a substantially nonpressure transferable thermoplastic resin base of a sofT vinyl chloride-acetate copolymer or mixture of such copolymers; 7 to 15 parts by weight of a nonvolatile liquid softener, immiscible with the base; 10 to 40 parts by weight of an agglomerative magnetic pigment, 0.1 to 5 parts by weight of a wetting agent, a substantial share of which is a wetting agent of the amine type; and a volatile liquid vehicle which is a solvent for the base and miscible with the softener in an amount sufficient to render the mixture readily coatable.
 8. The method of preparing a pressure sensitive ink-releasing element as set forth in claim 7 in which the setting of the layer is abetted by causing a stream of air to impinge on the exposed surface thereof. 